U.S. patent application number 11/047038 was filed with the patent office on 2006-08-03 for integrated base stations and a method of transmitting data units in a communications system for mobile devices.
This patent application is currently assigned to Lucent Technologies, Inc.. Invention is credited to Peter Bosch, Sape Mullender, Girija J. Narlikar, Louis G. Samuel, Lakshman N. Yagati.
Application Number | 20060171364 11/047038 |
Document ID | / |
Family ID | 36097671 |
Filed Date | 2006-08-03 |
United States Patent
Application |
20060171364 |
Kind Code |
A1 |
Bosch; Peter ; et
al. |
August 3, 2006 |
Integrated base stations and a method of transmitting data units in
a communications system for mobile devices
Abstract
Integrated base stations and a method of transmitting data units
in a communications system for mobile devices. In one embodiment,
an integrated base station includes a communications processor
having a protocol stack configured with a media access control
layer and a physical layer.
Inventors: |
Bosch; Peter; (New
Providence, NJ) ; Mullender; Sape; (North Plainfield,
NJ) ; Narlikar; Girija J.; (Basking Ridge, NJ)
; Samuel; Louis G.; (Swindon, GB) ; Yagati;
Lakshman N.; (Palo Alto, CA) |
Correspondence
Address: |
HITT GAINES, PC;LUCENT TECHNOLOGIES INC.
PO BOX 832570
RICHARDSON
TX
75083
US
|
Assignee: |
Lucent Technologies, Inc.
Murray Hill
NJ
|
Family ID: |
36097671 |
Appl. No.: |
11/047038 |
Filed: |
January 31, 2005 |
Current U.S.
Class: |
370/338 ;
370/412 |
Current CPC
Class: |
H04W 84/042 20130101;
H04W 28/14 20130101; H04W 80/00 20130101; H04W 88/08 20130101 |
Class at
Publication: |
370/338 ;
370/412 |
International
Class: |
H04Q 7/24 20060101
H04Q007/24 |
Claims
1. For use in a cellular communications network for mobile devices,
an integrated base station, comprising: a communications processor
including a protocol stack configured with a media access control
layer and a physical layer.
2. The integrated base station as recited in claim 1 wherein said
communications processor further includes a single buffer
associated with said protocol stack that is configured to queue
data units between a wired and wireless channel.
3. The integrated base station as recited in claim 2 wherein said
buffer is located on top of said protocol stack.
4. The integrated base station as recited in claim 2 wherein said
protocol stack is configured to generate timely-data for at least
one of said data units based on when a mobile device is selected
for transmission thereto.
5. The integrated base station as recited in claim 2 wherein said
protocol stack is configured to only generate timely-data for at
least one of said data units when a mobile device is selected for
transmission thereto.
6. The integrated base station as recited in claim 1 wherein said
at least one protocol layer is configured to notify a protocol
layer above said media access layer when a data unit processed by
said protocol stack is lost during transmission to a wireless
device.
7. The integrated base station as recited in claim 1 wherein said
protocol stack includes at least one layer above the media access
control layer selected from the group consisting of: a packet data
convergence protocol layer, and a radio link control layer.
8. The integrated base station as recited in claim 1 further
including at least one protocol layer interposing said media access
control layer and said physical layer.
9. The integrated base station as recited in claim 8 wherein said
at least one protocol layer is a High Speed Downlink Packet Access
layer.
10. The integrated base station as recited in claim 8 wherein said
at least one protocol layer is configured to provide packet
schedule functionality for wireless transmission to a mobile
device.
11. The integrated base station as recited in claim 8 wherein said
at least one protocol layer is configured to recognize transmission
failure of a data unit processed by said protocol stack.
12. The integrated base station as recited in claim 11 wherein said
at least one protocol layer is configured to notify at least one
other protocol layer of said transmission failure upon said
recognizing and said other protocol layer is configured to perform
appropriate actions upon said notification.
13. The integrated base station as recited in claim 12 wherein said
appropriate actions are selected from the group consisting of:
changing a protocol state variable, resetting a protocol state to
an initial state, and resetting a protocol state to a well known
protocol state.
14. The integrated base station as recited in claim 13 wherein said
changing a protocol state variable includes performing an action
selected from the group consisting of: enabling data compression,
disabling data compression, enabling header compression, disabling
header compression, transmitting certain data units, retransmitting
certain data units, refraining from transmitting certain data
units, refraining from retransmitting certain data units, notifying
a peer protocol entity, and modifying behavior of a timer.
15. An integrated base station for use with cellular communications
systems for mobile devices having a core network, comprising: a
communications processor having a protocol stack implemented in a
single processing entity and configured to produce data units
suitable for direct transmission between said core network and a
mobile device.
16. The integrated base station as recited in claim 15 wherein said
communications processor further includes a single buffer
configured to queue data units for said protocol stack.
17. The integrated base station as recited in claim 16 wherein said
buffer is located on top of said protocol stack.
18. The integrated base station as recited in claim 15 wherein said
protocol stack includes a layer configured to generate timed-data
for at least one of said data units based on when said mobile
device is selected for transmission thereto.
19. The integrated base station as recited in claim 15 wherein said
protocol layer is configured to recognize when a data unit
processed by said protocol stack is lost during transmission to
said mobile device without input from said mobile device.
20. The integrated base station as recited in claim 15 wherein said
protocol stack includes each of the following layers: a packet data
convergence protocol layer, a radio link control layer, a media
access control layer, and a physical layer.
21. The integrated base station as recited in claim 15 wherein said
communications system is selected from the group consisting of: a
Universal Mobile Telecommunications System, and a Code Division
Multiple Access 2000 system.
22. The integrated base station as recited in claim 15 wherein said
protocol stack includes a media access control layer configured to
perform independent transmission decisions based on channel
conditions to a wireless device.
23. In a communications system for mobile device, a method of
transmitting data units between a core network and a mobile device,
comprising: receiving a data unit at an integrated base station
from either said core network or said mobile device; providing said
data unit with required protocols at said integrated base station
for direct transmission between said core network and said mobile
device; and transmitting said data unit having said required
protocols to said core network or said mobile device.
24. The method as recited in claim 23 further comprising providing
a single buffer to queue said data unit between said core network
and said mobile device.
25. The method as recited in claim 24 further comprising providing
said single buffer on top of a protocol stack of said integrated
base station.
26. The method as recited in claim 23 further comprising generating
timed-data for said data unit based on when said mobile device is
selected for transmission thereto.
27. The method as recited in claim 23 further comprising
recognizing when said data unit is lost during transmission to said
mobile device without input from said mobile device.
28. The method as recited in claim 27 further comprising resetting
an internal protocol state upon said recognizing.
29. The method as recited in claim 27 further comprising
retransmitting said data unit upon said recognizing.
30. The method as recited in claim 29 wherein said required
protocols are provided by each of the following layers: a packet
data convergence protocol layer, a radio link control layer, a
media access control layer, and a physical layer.
Description
TECHNICAL FIELD OF THE INVENTION
[0001] The present invention is directed, in general, to
communications networks, and more specifically, to an integrated
base station, a communications system for mobile devices and a
method of transmitting data units in a communications system for
mobile devices.
BACKGROUND OF THE INVENTION
[0002] A cellular communications network typically includes a
variety of communication nodes coupled by wireless or wired
connections and accessed through different types of communications
channels. Each of the communications nodes includes a protocol
stack that processes the data transmitted and received over the
communications channels. Depending on the type of communications
system, the operation and configuration of the various
communication nodes can differ and are often referred to by
different names. Such communications systems include a Code
Division Multiple Access 2000 (CDMA2000) system and Universal
Mobile Telecommunications System (UMTS).
[0003] Considering UMTS as an example, a typical Universal Mobile
Telecommunications System (UMTS), includes a set of collaborating
components (i.e., physical machines with memory, processing
capacity and networking capabilities) that collectively bridge
voice circuits and Internet Protocol (IP) data packets over wired
and wireless connections to mobile devices such as a cellular
telephone. Generally, the mobile devices in a UMTS are referred to
as User Equipment (UE). Two such components in a UMTS include a
radio network controller (RNC) and a base station (Node B). In a
UMTS Terrestrial Radio Access Network (UTRAN), a core network (CN),
is responsible for bridging voice or data (IP) packets to a wired
network, such as, a telephony or IP network. A UTRAN is subdivided
into individual radio network systems (RNSs), where each RNS is
controlled by an RNC. The RNC is connected to a set of Node B
elements, each of which can serve one or several cells.
[0004] Each component of the UTRAN implements a part of the overall
protocol stack required for peer-to-peer communication between a
mobile device and the UTRAN. The required protocol stacks include a
Packet Data Convergence Protocol (PDCP) that provides header
compression for TCP/IP and RTP/UDP/IP packets, a Radio Link Control
(RLC) that provides Acknowledged Mode (AM), Unacknowledged Mode
(UM) and Transparent Mode (TM) transmissions and a Media Access
Control (MAC) that provides channelization and routing. An Iub
interface protocol stack between a RNC and a Node B is an example
of a conventional protocol stack of a UMTS.
[0005] In a conventional UTRAN, the PDCP, RLC and a portion of the
MAC layer execute in the RNC. For regular UMTS, the Node B
transmits PDCP/RLC/MAC Packet Data Units (PDUs) over wireless
circuits. A separate Radio Resource Control (RRC) layer controls
each protocol layer and executes in the RNC.
[0006] High Speed Downlink Packet Access (HSDPA) is a UMTS Release
5 extension that allows a Node B to make independent transmission
decisions based on channel conditions to a mobile device. A similar
packet schedule mode for wireless transmissions in a CDMA2000
system is DO or DV of a CDMA2000 protocol stack. A MAC-layer
extension that implements a High Speed scheduler for HSDPA
(MAC-HS), uses a multi-dimensional vector for scheduling to
optimize for bandwidth, frequency efficiency and latency. With
HSDPA, the RNC has limited control on the order in which the Node B
schedules the mobile device.
[0007] Additional problems associated with dividing the
functionality over the RNC and Node B include requiring multiple
(pipelined) staging buffers in the system causing a high end-to-end
latency and transmission of packets by the RLC and RRC layer that
contain information that may become stale or are superseded by a
newer version of the state. For instance, RLC-AM PDUs may contain
an acknowledgment state for a peer and RRC messages may contain
information for the mobile device to alter the state of the mobile
device. A packet or data unit containing the acknowledgment state
for the peer and the RRC messages can be referred to as
`timely-data.`
[0008] Timely-data is defined as data used for, or incorporated
into, data transmissions over a communications system and has a
value associated with a best performance of the communications
system that decreases with time. Thus, if a message containing
timely-data is delayed, the information contained in the message
may become obsolete and the usefulness of the message, when
received, will become less. An example of timely-data is data
pertaining to which packets were received (and, by implication,
which packets were not received) by a protocol entity. When such
packet-received data is delayed while new packets arrive, the
correctness of the packet-received data, and thus its usefulness,
will diminish.
[0009] When timely-data is queued inside the Node B on a bearer, as
can happen if the RNC has overestimated the outflow rate from the
Node B for regular circuits, or when the Node B simply does not
consider a mobile for transmission in HSDPA mode, a newer version
of the timely-data may be queued behind the original transmission.
This phenomenon wastes bandwidth, or worse older packets may
contain instructions for the mobile device that may already have
been retracted by a newer version of the timely-data message. A
provision in HSDPA enables packets to be removed from the
transmission queue after their lifetime has expired. Unfortunately,
this provision breaks RLC-AM since the RLC protocol assumes every
packet sent by an RLC-AM layer is received by the peer RLC-AM
layer.
[0010] Another problem associated with dividing the functionality
of the protocol stack over the RNC and Node B includes losing a
data packet in the system. In case there is a data packet loss in
the system (i.e., when the mobile suffers from a fade in HSDPA),
compression engines in the PDCP layer may need to be reset. Since
there is no interface provision between the Node B and the RNC to
indicate packet loss at the MAC-HS layer, resynchronization by the
PDCP sender is performed after receiving an indication for
resynchronization from the PDCP receiver. This can result in a
considerable time-lag between the packet drop and
resynchronization. While the sender is not resynchronized, all data
packets that are in flight cannot be successfully decoded resulting
in wasting of wireless bandwidth.
[0011] Furthermore, when an RLC Acknowledged Mode (RLC-AM) is used,
data packet loss at the HSDPA layer needs to be detected at the
RLC-AM receiver so that the RLC-AM transmitter can retransmit the
lost packet. Typically, a RLC-AM receiver detects the data packet
loss by receiving a subsequent data packet if one exists or by
timing out on a periodic timer. The receiver then sends a status
message to the RLC-AM transmitter, informing the transmitter of the
lost packets. This scheme introduces a delay between the time of
packet loss and the retransmission of the packet in RLC-AM. The
delay is usually a round trip time but can be at most the value of
the periodic timer (if the lost packet is the last in a
sequence).
[0012] Accordingly, what is needed is a system or method for
improving the communication of data in a communications system for
mobile devices. More specifically, what is needed in the art is an
improved system and method for transmitting data packets to mobile
devices.
SUMMARY OF THE INVENTION
[0013] To address the above-discussed deficiencies of the prior
art, the present invention provides integrated base stations (for
example, integrated UTRANs), and a method of transmitting data
units in a communications system for mobile devices. In one
embodiment, the integrated base station includes a communications
processor having a protocol stack configured with a media access
control layer and a physical layer.
[0014] In another aspect, the present invention provides another
integrated base station for use in a communications system for
mobile devices including a communications processor having a
protocol stack implemented in a single processing entity and
configured to produce data units suitable for direct transmission
between the core network and a mobile device.
[0015] For purpose of the present invention, direct transmission
shall mean buffering data units received from the core network to
match a difference in transmission speed of the core network and a
wireless channel and preparing the data units for transmission over
the wireless channel to a mobile device when the wireless channel
becomes available for transmission. Direct transmission, therefore,
allows transmitting a data unit between the core network and the
mobile device via a single processing entity. Thus, unlike present
mobile communications systems, a controller and base station are
not required. For example, in UMTS, a separate RNC and a Node B are
not required and in a CDMA2000 system, a separate RNC and a base
station are not required. Instead, the novel integrated base
station provides the proper protocols needed for communicating
between the wired and wireless domains.
[0016] Additionally, a data unit is defined for purposes of the
present invention as a general term referring to data that includes
a payload and associated headers or footers. In some communications
systems, the data unit may be known as, for example, a packet
(i.e., in UMTS) or a frame.
[0017] Thus, considering a UMTS for example, the present invention
collapses the functionality of an RNC and a Node B into a single
processing entity. The novel integrated base station allows PDCP,
RLC and MAC (also, possibly MAC-HS) to be executed on a single
machine. Since the protocol layers execute on a single machine,
inter-layer optimizations that can dramatically improve the
performance of the protocol stacks may be realized. One
specialization of this combining is to execute the protocol stacks
inside a single process on the integrated base station to ease
implementation of the optimizations and to minimize the number of
staging buffers between the protocol layers.
[0018] In one embodiment, each radio bearer contains one buffer for
data units, which resides between an IP and a PDCP layer. Thus, the
buffer is located above the PDCP layer in UMTS or above the PPP
layer when considering a CDMA2000 system. This buffer matches the
speed differences between wired communication links and wireless
channels and, more importantly, allows optimization of radio
transmission chains as compared to a multi-buffer, multi-system
solution typically deployed in a conventional UMTS. The single
buffer may only buffer IP packets that are destined for a
particular mobile device and allows the transmission of timed-data
when needed.
[0019] In yet another aspect, the present invention provides, for
use with a communications system for mobile devices, a method of
transmitting data units between a core network and a mobile device
including: (1) receiving data units at an integrated base station
from either said core network or said mobile device, (2) providing
said data units with required protocols at said integrated base
station for direct transmission between said core network and said
mobile device and (3) transmitting said data units having said
required protocols to said core network or said mobile device.
[0020] The foregoing has outlined preferred and alternative
features of the present invention so that those skilled in the art
may better understand the detailed description of the invention
that follows. Additional features of the invention will be
described hereinafter that form the subject of the claims of the
invention. Those skilled in the art should appreciate that they can
readily use the disclosed conception and specific embodiment as a
basis for designing or modifying other structures for carrying out
the same purposes of the present invention. For example, the
discussion regarding UMTS also applies to other cellular
communications systems, such as, CDMA2000. Those skilled in the art
should also realize that such equivalent constructions do not
depart from the spirit and scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] For a more complete understanding of the invention,
reference is now made to the following descriptions taken in
conjunction with the accompanying drawing, in which:
[0022] FIG. 1 illustrates a block diagram of one embodiment of a
communications system for mobile devices including an integrated
base station constructed according to the principles of the present
invention;
[0023] FIG. 2 illustrates a block diagram of another embodiment of
an integrated base station constructed according to the principles
of the present invention; and
[0024] FIG. 3 illustrates a flow diagram of an embodiment of a
method of transmitting data units between a core network and a
mobile device carried out according to the principles of the
present invention.
DETAILED DESCRIPTION
[0025] Referring initially to FIG. 1, illustrated is a block
diagram of one embodiment of a cellular communications system for
mobile devices, generally designated 100, including an integrated
base station 130 constructed according to the principles of the
present invention. The communications system 100 also includes a
core network 110 and a mobile device 120.
[0026] The communications system 100 may be a conventional
communications system such as a UMTS having multiple communications
nodes coupled through wireless or wired mediums. Of course, the
communications system 100 may be another type of communications
system, such as, a Global System for Mobile Communications (GSM).
Thus, one skilled in the art will understand that the discussion
regarding a UMTS also applies to other cellular communications
systems and components. For ease of discussion, the integrated base
station 130 is representative of the other integrated base stations
that are illustrated. One skilled in the art will also understand
that the communications system 100 may include additional
components or systems that are not illustrated or discussed but are
typically employed in a conventional communications system.
[0027] The core network 110 may be a conventional core network
configured to handle voice and (IP) back-haul issues. The core
network 110 consists of communication nodes or switches coupled via
connecting lines. As illustrated, the core network 110 connects the
integrated base station 130 to other integrated base stations and
conventional RNCs and Node Bs. Additionally, the core network 110
can provide gateways to other networks (ISDN, Internet, etc.).
[0028] The mobile device 120 may be a conventional cellular
telephone configured to operate in the communications system 100.
Thus, the mobile device 120 may be a UMTS enabled cellular
telephone. One skilled in the art will also understand that the
mobile device 120 may also be another wireless device that is
configured to operate in the communications system 100, such as, a
personal digital assistant (PDA), an MP3 player, etc.
[0029] The integrated base station 130 is coupled to the core
network 110 via a wired connection and to the mobile device 120 via
a wireless connection. The integrated base station 130 is
advantageously configured to include the functionality of a
conventional RNC and a conventional Node B in a single processing
entity. The integrated base station 130 includes a first data
interface 132, a second data interface 133 and a communications
processor 134 having a protocol stack 136, a buffer 138 and a Radio
Resource Control (RRC) layer. One skilled in the art will
understand that the integrated base station 130 includes additional
components or features that are not material to the present
invention but are typically employed in a conventional RNC or Node
B to transmit data units between a core network and a mobile
device.
[0030] The first data interface 132 is configured to transmit and
receive data units from the core network 110 and the second data
interface 133 is configured to transmit and receive data units from
the mobile device 120. The first data interface 132 includes
conventional components to transmit and receive data units over a
wired connection to the core network 110 and the second data
interface includes conventional components to transmit and receive
data units over a wireless connection to the mobile device 120. One
skilled in the art will understand the operation and configuration
of the first data interface 132 and the second data interface
133.
[0031] The communications processor 134 is configured to process
data units from the first data interface 132 and the second data
interface 133. The buffer 136 is configured to queue data units
from the core network 110 for the protocol stack 138. In FIG. 1,
the buffer 136 is located on top of the protocol stack 138.
[0032] The protocol stack 138 is configured to produce data units
suitable for direct transmission to the mobile device 120. Thus,
the protocol stack 138 provides a single location that receives
data units from the core network 110 and transmits the data units
with the proper protocols to the mobile device 120. The protocol
stack 138 includes a Packet Data Convergence Protocol (PDCP) layer,
a Radio Link Control (RLC) layer, a Media Access Control (MAC)
layer, and a High Speed Downlink Packet Access (HPSPA) layer. Of
course, one skilled in the art will understand that the protocol
stack 138 may include other or additional protocol layers in other
embodiments. In some embodiments, the HPSPA layer may not be
included in the protocol stack 138. Additionally, considering a
CDMA2000 system, the protocol stack 138 may be extended to include
such layer-2 protocol functionality as point-to-point protocol
(PPP) layer and radio link protocol (RLP) layer instead of the PDCP
layer and the RLC layer that is associated with a UMTS.
[0033] Due to the convergence of the protocol stack 138 into one
program, inter layer optimization can occur. For example, the RLC
and the RRC layers are configured to generate timed-data for the
data units based on when the mobile device is selected for
transmission thereto. With only a single queue and a collapsed
protocol stack 138, transmission data units can now be `pulled`
from the data queue whenever the base station decides to transmit a
data unit to a particular mobile device. For scheduled wireless
channels (i.e., HSDPA), this enables timely-data to be created only
when a particular mobile is addressed. This means that the
transmission always contains the most recent information available
and leads to a more efficient use of bandwidth and a more
responsive communications system 100.
[0034] Further optimization is realized with the protocol stack 138
configured to recognize when a data unit processed by the protocol
stack 138 is lost during transmission to the mobile device 120
without input from the mobile device 120. If there is a data unit
transmission error (in HSDPA), the HSDPA layer in the integrated
base station 130 can inform the RLC-AM layer of this event.
Henceforth, the RLC-AM layer can immediately reinitiate the
transmission of the lost data unit instead of waiting for a status
report or negative acknowledgement from the mobile device 120. The
RLC-AM layer can also determine not to retransmit the data unit
when otherwise the data unit would have been retransmitted.
[0035] Additionally, if there is a data unit transmission error (in
for example, HSDPA), the collapsed structure of the protocol stack
138 and the single buffer 136 allows the PDCP compression state to
be more easily reset. The integrated base station 130, therefore,
can determine an unsuccessful transmission of a data unit and allow
the PDCP layer to reset the protocol state of all affected radio
bearers. For example, the protocol state may be reset to a
well-known state or to an initial state.
[0036] Thus, upon recognizing a data unit is lost, appropriate
protocol layers of the protocol stack 138 may be notified and
appropriate actions may be performed. In addition to resetting
protocol states, the novel integrated base station 130 allows
changing protocol state variables. Changing protocol state
variables may include performing actions associated therewith
including: enabling/disabling data compression, enabling/disabling
header compression, transmitting/retransmitting certain data units,
refraining from transmitting/retransmitting certain data units,
notifying a peer protocol entity, and modifying behavior of a
timer. By recognizing a transmission failure and acting
appropriately, the present invention allows the higher layer
applications to recover sooner from losses of data units and can
reduce transmission of undecodable data units.
[0037] Turning now to FIG. 2, illustrated is a block diagram of one
embodiment of an integrated base station, generally designated 200,
constructed according to the principles of the present invention.
The integrated base station 200 includes a Radio Resource Control
(RRC) layer and a communications processor 220 having a protocol
stack 240 and a buffer 260. Of course, as illustrated in FIG. 1,
the RRC layer can be included within a communications processor in
some embodiments.
[0038] The communications processor 220 is configured to process
data units received over a communications network for mobile
devices. More specifically, the communications processor 220 is
configured to provide the needed protocols for transmitting a data
unit between a core network and a mobile device. One skilled in the
art will understand that the communications processor 220 includes
additional components that are not material to the invention and
are not illustrated or discussed.
[0039] The protocol stack 240 includes a PDCP layer, a RLC layer, a
MAC layer and a physical layer. Integrated within the MAC layer is
the functionality of a HSDPA layer. Thus, the MAC layer is
configured to perform independent transmission decisions based on
channel conditions to a wireless device. Of course, as illustrated
in FIG. 1, a HSDPA layer can interpose the MAC layer and the
physical layer. Additionally, in other cellular communications
systems, the MAC layer may have other packet schedule modes
integrated therein. For example, in a CDMA2000 system, the MAC
layer may include the functionality of a DO or DV layer.
[0040] The buffer 260 may be a conventional buffer configured to
queue data units between a wired and wireless channel. The buffer
260 is located on top of the protocol stack 240. Locating the
buffer 260 above the PDCP layer allows the buffer 260 to queue
uncompressed data units. If the buffer 260 is located in other
locations, restarting a PDCP resynchronization procedure is more
difficult. Thus, the buffer 260 resides between the IP and PDCP
layers to provide a single queue for data units. The buffer 260 is
configured to match speed differences between the wired and
wireless domains, but more importantly allows unique optimization
of radio transmission chains and provides distinct advantages over
a multi-buffer, multi-system solution as deployed in a conventional
UMTS without an integrated base station of the present
invention.
[0041] Additionally, end-to-end latencies are reduced since there
is no staging of data through multiple queues. In a regular UTRAN,
data units are delayed as they are staged through the various
buffers in the UTRAN components before they are transmitted over a
wireless channel. However, in a single-machine, single-buffer
system of the present invention, a data unit may only be delayed by
the time it is queued in the single buffer 260. There is no staging
time for a data unit to traverse a number of queues.
[0042] With only a single queue and a collapsed stack, transmission
data units can now be `pulled` from the buffer 260 whenever the
integrated base station 200 decides to transmit a data unit to a
particular mobile device. For scheduled wireless channels (i.e.,
HSDPA), this enables timely-data to be created only when a
particular mobile device is addressed. This means that the
transmission always contains the most recent information available
and leads to a more efficient use of bandwidth and a more
responsive mobile communications system.
[0043] Thus, when a mobile device is selected for data
transmission, precisely enough, where enough depends on the
wireless channel conditions and coding schemes, data units are
pulled from the single data buffer 260. At this particular
instance, the MAC, RLC and PDCP stack is executed for the radio
bearer and at this particular instance RRC and RLC state
information is generated. When needed, the data units are header
compressed in the PDCP layer. Since timely-data is only generated
at the latest possible instance, the timely-data cannot become
stale or be superseded by a newer version.
[0044] The integrated base station 200 may employ RLC-UM or RLC-AM
when transmitting data units. When employing RLC-UM for
communication, a MAC-HS layer notifies the compression layer (PDCP)
when a data unit is lost in the downlink. The PDCP, therefore, can
reset its internal compression schemes and resynchronize with a
remote peer. The latter implies that resynchronizing the
compression state is performed much sooner and does not require the
receiver to signal the sender of a lost data unit. When employing
RLC-AM for communication, the PDCP layer does not need to reset if
a data unit is dropped. Instead, the HSDPA layer notifies the
RLC-AM layer of this event and the RLC-AM layer can retransmit the
data unit without waiting for a status message from the mobile
device.
[0045] Turning now to FIG. 3, illustrated is a flow diagram of an
embodiment of a method of transmitting data units between a core
network and a mobile device, generally designated 300, carried out
according to the principles of the present invention. The method
begins with an intent to transmit a data unit to a mobile device in
a step 305.
[0046] After beginning, a data unit is received at an integrated
base station from a core network in a step 310. The data unit is
received via a wired connection.
[0047] After the data unit is received, a buffer is provided to
queue the data unit between the core network and the mobile device
in a step 320. The buffer is advantageously provided on top of a
protocol stack that is employed to process the data unit.
[0048] After providing the buffer, a determination is then made if
a mobile device has been selected to receive the data unit in a
decisional step 330. If a mobile device has been selected, then
timed-data is generated for the data unit in a step 340. If a
mobile device has not been selected, the method returns to step
320.
[0049] After generating the timed-data, required protocols are
added to the data unit in a step 350. The required protocols are
those needed for direct transmission between the core network and
the mobile device. Typically, the required protocols are provided
by a protocol stack of an integrated base station. In one
embodiment, the required protocols are provided by a PDCP layer, a
RLC layer and a MAC layer.
[0050] After providing the required protocols, the data unit is
transmitted with the required protocols to the mobile device in a
step 360.
[0051] The method 300 then determines if the packet was lost during
transmission in a second decisional step 370. If the packet was
lost, the method continues to a step 375 that provides a
transmission failure notification. When timed-data is lost, the
next higher layer is notified. If the notified layer cannot solve
the transmission problem (perform an appropriate action to solve),
the next higher layer is notified. Thus, each layer that does not
solve the dropped packet event notifies the layer above it of the
event. After providing the transmission failure notification, the
method returns to step 330 and continues. If the data unit was not
lost, the method ends in a step 380.
[0052] Although the present invention has been described in detail,
those skilled in the art should understand that they can make
various changes, substitutions and alterations herein without
departing from the spirit and scope of the invention in its
broadest form.
* * * * *